Gas-hydraulic system for crushers



Dec. 24, 1968 T. F. GUNDLACH GAS-HYDRAULIC SYSTEM FOR CRUSHERS 2 Sheets- Sheet 1 Filed Nov. 14, 1966 FIG. I

FIG. 2

INVENTOR THEODORE F. GUNDLACH ATTORNEYS Dec. 24, 1968 T. GUNDLACH 3,417,928

GASHYDRAULIC SYSTEM FOR CRUSHERS Filed Nov. 14, 1966 3 Sheets-Sheet 2 so "YI F'IIIIZ' FIG. 3

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85 |-vs-ro|z THEODORE F. GUNDLACH QO'MGMA ATTORNEYS United States Patent Illinois Filed Nov. 14, 1366, Ser. No. 593,757 Claims. (Cl. 24132) This invention relates generally to a gas-hydraulic system for a material crusher, and more particularly to an improved means for maintaining and regulating the spacing between crushing elements and for enabling the spacing to increase selectively upon exceeding a predetermined load.

An important objective is achieved by the provisions of a gas-hydraulic means in a material crusher having a pa r of spaced crushing elements, at least one of which is movable with respect to the other to adjust the spacing between crushing surfaces. The gas-hydraulic means in eludes a hydraulic fluid in a housing at one side of -a piston slidably mounted in the housing, the hydraulic fiuid opr posing relative movement of the crushing elements to- Ward each other to maintain a predetermined spacing between the crushing elements, and includes a gaseous fluid under pressure in the housing at the other side of the piston opposing movement of the crushing elements away from each other up to a predetermined load.

Another important object is afforded by the structural arrangement in which the piston of the gas-hydraulic means is operatively connected to the movable crushing element so as to move therewith, while the housing is attached to a fixed portion of the crusher.

Still another important objective is realized by the provision of a hydraulic pump operatively connected to the housing at one side of the piston for controlling the volume of hydraulic fluid in the housing, and by the provision of a supply of gaseous fluid under pressure operatively connected to the housing at the other side of the piston for determining the predetermined load.

An important object is attained by journalling the pair of crushing elements at each of their axial ends for rotation on a crusher frame. The piston and housing of the gas-hydraulic means operatively interconnect one axial end of the movable crushing element with the frame, while means operatively interconnects the other axial end of the movable crushing element with the gas-hydraulic means so that the axial ends of the movable crushing element move in unison.

Another important objective is provided by the structural arrangement in which a second piston and second housing operatively interconnect the other axial end of the movable crushing element with the frame. Hydraulic fluid in the second housing at one side of the second piston opposes relative movement of the crushing elements toward each other to maintain the predetermined spacing between the crushing elements, and gaseous fluid under pressure in the second housing at the other side of the piston opposes relative movement of the crushing elements away from each other up to the predetermined load. A control means is operatively connected to the hydraulic and gaseous sides of the piston in each housing.

Yet another important objective is achieved in that the 3,417,928 Patented Dec. 24, 1968 "ice control means includes a hydraulic line interconecting the hydraulic sides of the pistons, while a hydraulic pump is operatively connected to the hydraulic line for moving the pistons in unison in response to the volume of hydraulic fluid introduced into or withdrawn from the housings. In addition, the control means includes a gas line interconnecting the gaseous sides of the pistons, while a reservoir of gaseous fluid under pressure is operatively connected to the gas line for selectively feeding gaseous fluids into the housings.

An important object is afforded by the provision of a second pair of crushing elements that cooperate with the first pair of crushing elements to provide a two-stage crusher. Each pair of crushing elements are journalled at their axial ends for rotation on the frame, while one of the pair of crushing elements are movable relative to the other. The gas-hydraulic means includes an associated piston and housing operatively interconnecting the movable crushing element of each stage to the frame for controlled movement.

Another important objective is realized in that the control means introduces a predetermined volume of hydraulic fluid into the housing against which the piston bears in fixing the spacing between the crushing elements under loading of the gaseous fluid on the opposite side of the piston. The piston compresses the gaseous fluid in the housing as the crushing elements move relatively apart and causes a cavitational effect at the other side of the piston by increasing the volume of the hydraulic side of the housing while maintaining substantially the same volume of hydraulic fluid in the housing.

It is a further objective to provide a gas-hydraulic system in a material crusher that is simple and durable in construction, economical to manufacture and assemble, highly eflicient in operation, and which can be readily adjusted by anyone with little or no instruction.

The foregoing and numerous other objects and advantages of the invention will more clearly appear from the following detailed description of several preferred embodiments, particularly when considered in connection with the accompanying drawings, in which:

FIG. 1 is an elevational view of one side of a typical roll type crusher illustrating the application of the present invention thereto;

FIG. 2 is a diagram of the gas-hydraulic system utilized in the crusher of FIG. 1;

FIG. 3 is an elevational view of one side of another typical roll type crusher illustrating the application of the present invention thereto; and

FIG. 4 is a diagram of the gas-hydraulic system utilized in the crusher of FIG. 3.

Referring now by characters of reference to the drawings, and first to the roll type crusher illustrated in FIG. 1, it will be understood that the crusher includes a frame 10 of any suitable construction upon which are mounted a pair of conventional crushing rolls 11 and 12, constituting the first stage of a two-stage crusher. The crushing rolls 11 and 12, constituting crushing elements, are journalled at their respective ends in two pair of journal boxes 13 and 14 respectively, each pair being laterally spaced from the other atop frame 10. The crushing rolls 11 and 12 have crushing surfaces adapted by movement of the crushing rolls 11 and 12 relative to each other to crush material therebetween. As will be later understood, at least one crushing roll 11 is movable with respect to the other roll 12 to adjust the spacing between the crushing surfaces.

The frame includes a fixed crusher section generally indicated by 15 and a relatively movable crusher section referred to by 16. The fixed crusher section 15 includes a stationary base rail 17 and a supported hopper portion 20. The journal boxes 14 are rigidly fixed to the frame 10 of the movable crushing section 16 by horizontally extending beams 21.

The movable crusher section 16 includes a platform 22 supported by wheels 23 on the base rail 17 of the stationary crusher section 15. The journal boxes 13 are rigidly fixed to the frame 10 of the movable crusher section 16 by horizontally extending beams 24. A hopper portion 25 is supported by the frame 10 of the movable crusher section 16 and complements the coacting hopper portion 20.

Any suitable means, such as that provided by the power unit 26, may be employed to drive the rolls 11 and 12 in opposite directions.

The second stage of the two-stage crusher includes a pair of conventional crushing rolls 27 and 30 journalled at their respective ends in two pair of journal boxes 31 and 32 respectively. The crushing rolls 27 and 30, constituting crushing elements, have crushing surfaces and are adapted by movement relative to each other to crush material therebetween. At least one crushing roll 27 is movable with respect to the other roll 30 to adjust the spacing between the crushing surfaces. The crushing rolls 27 and 30 are located immediately below the crushing rolls 11 and 12 respectively of the first stage so as to receive and crush the discharge from the first stage.

The journal boxes 32 are fixed to the frame 10 of the K stationary crusher section 15. The journal boxes 31 are fixed to the frame 10 of the movable crusher section 16.

Any suitable means, such as the power unit 33, may be employed to drive the crushing rolls 27 and 30 in opposite directions.

By movement of the movable crushing section 16 relative to the stationary crushing section 15, the position of the movable crushing rolls 11 and 27 can be selectively adjusted relative to the crushing rolls 12 and 30 to adjust the spacing between the crushing surfaces of the associated paired rolls.

A gas-hydraulic means is utilized to adjust the position of the movable crushing rolls 11 and 27. Specifically, the gas-hydraulic means will move the movable crushing section 16 relative to the stationary crushing section 15.

The gas-hydraulic means includes a piston-housing assembly at each side of the crusher. One of these pistonhousing assemblies is illustrated in FIG. 1, but an identical assembly is utilized on the reverse side. Consequently, a detailed description of one such assembly will suflice for the other.

The piston-housing assembly includes a piston 34 slidably mounted in a housing 35. The piston 34 includes a shank 36 extending outwardly of the housing and attached by a yoke 37 to a bracket 40 that is fixed to the frame 10 of the movable crusher section 16. The opposite end of the housing 35 is fixed by a pivot pin 41 to the frame 10 of the stationary crusher section 15.

A hydraulic fluid 42 in the housing 35 at one side of the piston 34 opposes relative movement of the paired crushing rolls 11 and 12 and of the paired crushing rolls 27 and 30 toward each other, and maintains the predetermined spacing between such paired crushing rolls 11 and 12 and paired crushing rolls 27 and 30. A gaseous fluid 43 under pressure in the housing 35 at the other side of the piston 34 opposes movement of the paired crushing rolls 11 and 12 and of the paired crushing rolls 27 and 30 away from each other up to a predetermined load.

The system of the gas-hydraulic means is illustrated in FIG. 2. The control means operatively connected to the hydraulic and gaseous sides of the piston 34 in each housing 35 includes a hydraulic line 44 operatively interconnecting the hydraulic sides of each piston 34. A hydraulic pump 45 is operatively connected to the hydraulic line 44 for moving the pistons 34 in unison in response to the volume of hydraulic fluid introduced into or withdrawn from the housings 35. The control means includes a gas line 46 that operatively interconnects the gaseous sides of the pistons 34. A gas tank 47, constituting a reservoir of gaseous fluid under pressure, is operatively connected to the gas line 46 through a regulator 50 for selectively feeding gaseous fluid into the housings 35. An auxiliary tank 51 is operatively interconnected with both the gas line 46 and the primary gas tank 47, the auxiliary tank 51 providing an additional reservoir.

It is thought that the functional advantages of the gashydraulic system have become fully apparent from the foregoing detailed description of parts, but for completeness of disclosure, it will be understood that the hydraulic pump 45 in FIG. 2 is actuated to introduce a predetermined volume of hydraulic fluid 42 into each of the housings 35 at one side of the associated piston 34. The volume of the hydraulic fluid 42 in the housings 35 will de termine the predetermined, selected and adjusted spacing between the associated pairs of crushing rolls 11-12 and 27-30. By introducing a volume of hydraulic fluid 42 into the housings 35, the hydraulic fluid 42 tends to extend the associated piston rod 36 and thereby move the movable crushing rolls 11 and 27 away from their associated stationary crushing rolls 12 and 30 respectively. Conversely, by withdrawing hydraulic fluid 42 from the housings 35, the piston rod 36 will tend to be retracted under the pressure of the gaseous fluid 43 so as to move the movable crushing rolls 11 and 27 relatively toward their associated stationary crushing rolls 12 and 30 respectively.

The gaseous fluid 43 at the other side of the pistons 34 in the piston housings 35 is placed under a predetermined pressure as determined and regmlated by the regulator 50, the geseous fluid 43 being fed from the gas tank 47. The pressure of the gaseous fluid 43 urges the pistons 34 into a predetermined position against a predetermined volume of hydraulic fluid 42. The pressure of the gaseous fluid 43 determines the predetermined load which will be opposed by the gaseous fluid 43 by movement of the paired crushing rolls 11 and 12 and of the paired crush ing rolls 27 and 30 relatively away from each other.

When a noncrushable object passes between either pair of the crushing rolls 1112 or 27-30, the object will move the movable crushing roll 11 or 27 away from its associated stationary crushing roll 12 or 36 respectively against the resilient loading of the gaseous fluid 43 in the housings 35. As the associated pairs of crushing rolls move relatively apart, the pistons 34 compress the gaseous fluid 43 in the housings 35 and cause a cavitational effect at the other side of the pistons 34 by increasing the volume of the hydraulic side in the housings 35 while maintaining substantially the same volume of hydraulic fluid 42. When the noncrushable object has passed through the associated pairs of crushing rolls, the pressure of the gaseous fluid 43 will immediately retract the pistons 34 to the predetermined position determined by the fixed volume of hydraulic fluid 42. Thereby, the movable crushing rolls 11 and 27 will be returned to the initial position to maintain the predetermined spacing with their associated stationary crushing rolls 12 and 30 respectively.

Another type of two-stage crusher is illustrated in FIG. 3, and the gas-hydraulic system utilized in such crusher is illustrated in FIG. 4.

The roll type crusher of FIG. 3 incorporates a frame 52 of suitable construction upon which are mounted a pair of conventional crushing rolls 53 and 54, constituting crushing elements of the first stage, journalled at their respective ends in two pair of journal boxes 55 and 56 respectively. The journal boxes 56 are rigidly fixed to frame 10. The journal box 55 of the movable crushing roll 53 is slidably mounted between horizontal beams 57 and 60. Any suitable means (not shown) may be employed to drive the crushing rolls 53 and 54 in Opposite directions, and an appropriate feed hopper 61 is mounted above and about the crushing rolls 53 and 54.

The crushing rolls 53 and 54 have crushing surfaces adapted by movement of the crushing rolls 53 and 54 relative to each other to crush material therebetween. The crushing roll 53 of the first stage is movable with respect to the stationary crushing roll 54 to adjust the spacing between the crushing surfaces.

The second stage of the crusher illustrated in FIG. 3 is similarly constructed. For example, the second stage includes a pair of crushing rolls 62 and 63 journalled at their respective ends in two pair of journal boxes 64 and 65 respectively. The journal boxes 65 are fixed to frame 10. The journal boxes 64 are slidably mounted to the frame similar to the mounting of the movable journal boxes 55 of the first stage, previously described. Again, suitable drive means (not shown) may be employed to drive the crushing rolls 62 and 63 in opposite directions.

The crushing rolls 62 and 63 are located immediately below the cooperating crushing rolls 53 and 54 of the first stage so as to receive the discharge from the first stage. The crushing rolls 62 and 63 have crushing surfaces adapted by movement of the crushing rolls 62 and 63 relative to each other to crush material therebetween. The crushing roll 62 is movable with respect to the stationary crushing roll 63 to adjust the spacing between the crushing surfaces.

A gas-hydraulic means is utilized and is operatively associated with the movable crushing rolls 53 and 62 of the two stages respectively. The gas-hydraulic means includes a piston-housing assembly operatively associated with each journal box 55 of the movable crushing roll 53 and with each journal box 64 of the movable crushing roll 62. The piston-housing assemblies are identical so that a detailed description of one will suflice for the others. FIG. 3 illustrates a pair of the piston-housing assemblies utilized at one side of the crusher. It will be readily understood that an identical pair of piston-housing assemblies are utilized on the opposite side. The diagram of the gashydraulic means illustrated in FIG. 4, discloses all four piston-housing assemblies.

Each piston-housing assembly includes a piston 66 slidably mounted in an elongate housing 67 mounted securely to the frame column 70 at one end of the guideway between the horizontal beams 57 and 60. The piston 66 has a rod 71 fixed by bracket 72 to the movable journal box 55. Movement of the piston 66 in the housing 67 causes a slidable, corresponding movement of the journal box 55 and the associated movable crushing roll 53.

A hydraulic fluid 73 is disposed in the housing 67 at one side of the piston 66 opposing relative movement of the crushing rolls 53 and 54 toward each other, thereby maintaining the predetermined spacing between the crushing rolls 53 and 54. A gaseous fluid 74 under pressure is disposed in the housing at the other side of the piston 66 which opposes movement of the crushing rolls 53 and 54 away from each other up to a predetermined load.

The journal boxes 55 of the movable crushing roll 53 are effectively and operatively interconnected by an align ment mechanism referred to by 75. This alignment mechanism 75 includes a rod 76 pivotally mounted by bracket 77 to the journal box 55. The rod 76 is connected by a turn-buckle 80 to a crankarm. The crankarm 81 is fixed to and rotatable with a cross-shaft 82. The cross-shaft 82 operatively interconnects a similar rod 76, turn-buckle 80 and crankarm 81 operatively associated with the journal box 55 at the opposite side of the crusher. A similar type of alignment means referred to at 83 operatively inter- 6 connects the journal boxes 64 of the movable crushing roll 62 of the second stage.

The control means operatively connected to the hydraullic and gaseous sides of the piston 66 in each of the housings 67 is shown in the diagram of FIG. 4. The control means for the gas-hydraulic means includes a hydraulic pump 84 having a valve manifold 85. A pair of hydraulic lines 86 are operatively connected to the pump 84 through the valve manifold 85, and flow through such lines 86 is regulated by valve member 87. The hydraulic lines 86 operatively communicate with the hydraulic sides of the housings 67 of the first stage of the crusher. Another pair of hydraulic lines 90 are operatively connected to the pump 84 through the valve manifold 85, and flow through such lines 90 is controlled by the valve member 91. The hydraulic lines 90 are operatively in communication with the hydraulic sides of the housings 67 of the second stage of the crusher.

A tank 92, constituting a supply of gaseous fluid under pressure, is connected by gas line 93 through a regulator 94. The gas line 93 communicates with a gas feed line 95 from which branch gas lines 96 communicate with the gaseous sides of the housing 67 of the first stage of the crusher, and from which branch gas lines 97 communicate with the gaseous sides of the housings 67 of the second stage of the crusher.

It is thought that the functional advantages of the gashydraulic system disclosed in FIGS. 3 and 4 are apparent from the foregoing detailed description of parts, but for completeness of disclosure, a brief description of the operation is given.

First, the predetermined spacing of the crushing rolls 53 and 54 of the first stage is attained by manipulating the valve member 87 to introduce hydraulic fluid through lines 86 into the hydraulic sides of the housings 67 of such first stage. As the volume of hydraulic fluid increases in these piston-housings 67, the pistons 66 move the crushing roll 53 in a direction away from its relatively stationary crushing roll 54. By withdrawing the hydraulic fluid from the hydraulic sides of such housings 67 through the hydraulic lines 86 back into the reservoir of the pump 84, the movable crushing roll 53 will move toward its cooperating stationary crushing roll 54, as the piston 66 is moved under the pressure of the gaseous fluid 74 in such piston-housings 67. It will be understood that the opposite axial ends of the movable crushing roll 53 will be moved in unison.

The gaseous fluid 74 is introduced into the gaseous sides of the housings 67 of the first stage through the branch gas lines 96 and from the common gas feed line 95 and gas line 93 from the tank 92. The gaseous fluid 74 in the housings 67 is maintained under a predetermined pressure on the one side of the pistons 66, the predetermined pressure determining the load above which the pistons 66 will move to compress the gaseous fluid 74 and thereby permit movement of the movable crushing roll 53 away from the relatively stationary crushing roll 54.

When a noncompressible object passes between the crushing rolls 53 and 54, and as a result the movable crushing roll 53 is subjected to a load greater than the predetermined value, the crushing roll 53 will move away from the stationary crushing roll 54 and the pistons 66 will compress the gaseous fluid 74 in the housings 67. This movement of the pistons 66 causes a cavitational effect at the other side of the pistons 66 by increasing the volume of the hydraulic sides of the housings 67 while maintaining substantially the same volume of hydraulic fluid in such housings 67. Immediately after the noncompressible object passes through the crushing rolls 53 and 54, the pressure of the gaseous fluid 74 will urge the pistons 66 in a direction so as to move the crushing roll 53 toward its cooperating stationary crushing roll 54. The limit of such return movement of pistons 66 is fixed by the volume of the noncompressible hydraulic fluid 73. Thus, the movable crushing roll 53 is returned quickly and positively to its predetermined spacing with the relatively stationary crushing roll 54.

The movement of the movable crushing roll 62 in the second stage and its control by the gas-hydraulic means is essentially the same as that previously described with respect to crushing roll 53 of the first stage. Briefly, hydraulic fluid 73 is introduced into the hydraulic sides of the housings 67 through the hydraulic lines 90 by manipulation of the valve member 91. The volume of the hydraulic fluid 73 in these housings determine the desired spacing of the crushing rolls 62 and 63. Gaseous fluid 74 under pressure is introduced into the housings 67 at the opposite sides of the pistons 66 from the tank 92 through the gas lines 93, 95 and 97.

When a noncompressible object passes through the crushing rolls 62 and 63 and the predetermined load is exceeded as determined by the pressure of the gaseous fluid 74, the gaseous fluid 74 will be compressed by the pistons 66 to allow movement of the movable crushing roll 62. As the gaseous fluid 74 is compressed in the housings 67 as the crushing rolls 62 and 63 move relatively apart, the pistons 66 cause a cavitational effect at the other side of the pistons 66 by increasing the volume of the hydraulic side in such housings 67 while maintaining substantially the same volume of hydraulic fluid 73. Immediately after the noncrushable object has passed through the crushing rolls 62 and 63, the movable crushing roll 62 will return to its initial position and predetermined spacing with the relatively stationary crushing roll 63, as the pistons 66 are urged under the pressure of the gaseous fluid 74 to a position as determined by the volume of hydraulic fluid 73.

It will be understood that the crushing rolls 53 and 54 of the first stage and the crushing rolls 62 and 63 of the second stage can be regulated independently of the other through the gas-hydraulic means so that the rolls of each stage can have different predetermined spacing and different predetermined loads, above which, movement of the movable rolls can be attained.

Although the invention has been described by making detailed reference to two preferred embodiments, such detail is to be understood in an instructive, rather than in any restrictive sense, many variants being possible within the scope of the claims hereunto appended.

I claim as my invention:

1. In a material crusher:

(a) a pair of spaced crushing elements having crushing surfaces and adapted by movement of the crushing elements relative to each other to crush material therebetween,

(b) at least one of the crushing elements being movable with respect to the other to adjust the spacing between the crushing surfaces, and

(c) a gas-hydraulic means operatively associated with the movable crushing element, the gas-hydraulic means including at least one piston housing,

(d) a piston slidably mounted in the housing,

(e) a hydraulic fluid in the housing at one side of the piston opposing relative movement of the crushing elements toward each other to maintain the predetermined spacing between the crushing elements, and

(f) a gaseous fluid under pressure in the housing at the other side of the piston opposing movement of the crushing elements away from each other up to a predetermined load.

2. A material crusher as defined in claim 1, in which:

(g) the piston of the gas-hydraulic means is operatively connected to the movable crushing element so as to move therewith, and

(h) the housing is attached to a fixed portion of the crusher.

3. A material crusher as defined in claim 1, in which:

(g) a hydraulic pump is operatively connected to the housing at the said one side of the piston for controlling the volume of hydraulic fluid in the housing, and

(h) a supply of gaseous fluid under pressure is operatively connected to the housing at the said other side of the piston for determining the predetermined load.

4. A material crusher as defined in claim 1, in which:

"(g) the crusher includes a frame,

(h) the pair of crushing elements are journalled at each of their axial ends for rotation on the frame,

(i) the piston and housing operatively interconnect one axial end of the movable crushing element with the frame, and

(j) means operatively interconnect the other axial end of the movable crushing element with the gas-hydraulic means so that the axial ends of the movable crushing element move in unison.

5. A material crusher as defined in claim 1, in which:

(g) the crusher includes a frame,

(h) the pair of crushing elements are journalled at each of their axial ends for rotation on the frame,

(i) the piston and housing operatively interconnect one axial end of the movable crushing element with the frame,

(j) the gas-hydraulic means includes a second housing,

(k) a second piston is slidably mounted in the second housing,

(1) a hydraulic fluid is in the second housing at one side of the second piston opposing relative movement of the crushing elements toward each other to maintain the predetermined spacing between the crushing elements,

(In) a gaseous fluid under pressure is in the second housing at the other side of the second piston opposing relative movement of the crushing elements away from each other up to the predetermined load,

(11) the second piston and second housing operatively interconnect the other axial end of the movable crushing element With the frame, and

(0) control means is operatively connected to the hydraulic and gaseous sides of the piston in each housing.

6. A material crusher as defined in claim 5, in which:

(p) the control means includes a hydraulic line interconnecting the hydraulic sides of the pistons,

(q) a hydraulic pump is operatively connected to the hydraulic line for moving the pistons in unison in response to the volume of hydraulic fluid introduced into or withdrawn from the housings,

(r) a gas line interconnects the gaseous sides of the pistons, and

(s) a reservoir of gaseous fluid under pressure is operatively connected to the gas line for selectively feeding gaseous fluid into the housings.

7. A material crusher as defined in claim 1, in which:

(g) the crusher includes a frame,

(h) the pair of crushing elements are journalled at each of their axial ends for rotation on the frame,

(i) a second pair of crushing elements are journalled at each of their axial ends for rotation on the frame to provide a two-stage crusher, one of the pair of crushing elements being movable relative to the other, and

(j) the gas-hydraulic means includes an associated piston and housing operatively interconnecting the movable crushing element of each stage to the frame.

8. A material crusher as defined in claim 7, in which:

(k) an associated piston and housing operatively interconnect each axial end of each movable crushing element with the frame, and

(1) control means is operatively connected to the hydraulic and gaseous sides of the piston in each housing.

9. A material crusher as defined in claim 8, in which:

(in) the control means includes a hydraulic line interconnecting the hydraulic sides of the pistons in each stage of the crusher,

(n) a hydraulic pump is operatively connected to the hydraulic line of each stage for moving the pistons in unison in response to the volume of hydraulic fluid introduced into or withdrawn from the housings.

(o) a gas line interconnects the gaseous sides of the pistons in each stage of the crusher, and

(p) a reservoir of gaseous fluid under pressure is operatively connected to the gas line for selectively feeding gaseous fluid into the housings.

10. A material crusher as defined in claim 1, in which:

(g) the piston includes a piston head slidably mounted in the housing,

(h) the gaseous fluid is at one side of the piston head,

(i) the hydraulic fluid is at the other side of the piston head,

(j) control means introduces a predetermined volume of hydraulic fluid into the housing against which the piston head bears in fixing the spacing between the crushing elements under loading of the gaseous fluid on the opposite side of the piston head, and

(k) the piston head compresses the gaseous fluid in the housing as the crushing elements move relatively apart and causes a cavitational etfect at the other side of the piston head by increasing the volume of the hydraulic side while maintaining substantially the same volume of hydraulic fluid.

References Cited UNITED STATES PATENTS 3,038,670 6/1962 Becker 241290 X 3,099,406 7/ 1963 Kautz 24132 3,315,901 4/1967 Pollitz 241290 X 3,315,902 4/ 1967 Pollitz 241-231 WILLIAM S. LAWSON, Primary Examiner.

US. Cl. X.R. 

1. IN A MATERIAL CRUSHER: (A) A PAIR OF SPACED CRUSHING ELEMENTS HAVING CRUSHING SURFACES AND ADAPTED BY MOVEMENT OF THE CRUSHING ELEMENTS RELATIVE TO EACH OTHER TO CRUSH MATERIAL THEREBETWEEN, (B) AT LEAST ONE OF THE CRUSHING ELEMENTS BEING MOVABLE WITH RESPECT TO THE OTHER TO ADJUST THE SPACING BETWEEN THE CRUSHING SURFACES, AND (C) A GAS-HYDRAULIC MEANS OPERATIVELY ASSSOCIATED WITH THE MOVABLE CRUSHING ELEMENT, THE GAS-HYDRAULIC MEANS INCLUDING AT LEAST ONE PISTON HOUSING, (D) A PISTON SLIDABLY MOUNTED IN THE HOUSING, (E) A HYDRAULIC FLUID IN THE HOUSING AT ONE SIDE OF THE PISTON OPPOSING RELATIVE MOVEMENT OF THE CRUSHING ELEMENTS TOWARD EACH OTHER TO MAINTAIN THE PREDETERMINED SPACING BETWEEN THE CRUSHING ELEMENTS, AND (F) A GASEOUS FLUID UNDER PRESSURE IN THE HOUSING AT THE OTHER SIDE OF THE PISTON OPPOSING MOVEMENT OF THE CRUSHING ELEMENTS AWAY FROM EACH OTHER UP TO A PREDETERMINED LOAD. 